Electrical relay circuitry for magnetizing systems and the like



United States Patent 3,398,328 ELECTRICAL RELAY CIRCUITRY FOR MAGNE-TIZING SYSTEMS AND THE LIKE Leonard Piekarski, Pomona, Calif., assignorof one-fourth each to Irving B. Collins, Los Angeles, VeronicaWhitesides, Culver City, T. A. Smith, Long Beach, and Carroll E. Isham,Buena Park, Calif.

Filed Apr. 21, 1966, Ser. No. 544,207 Claims. (Cl. 317-123) Thisinvention relates to improved electrical apparatus for opening andclosing an electrical circuit, with certain features of the apparatusbeing in some respects especially useful for momentarily closing acircuit to a unit which is responsive to or actuable by an electricalimpulse of short duration. For instance, equipment embodying theinvention is very useful for closing and then'opening the circuit to amagnetizing coil, so that a rapid surge of current may pass through thecoil for magnetizing elements placed therein. For simplicity ofdiscussion, the invention will be described hereinafter primarily asapplied to the energization of such magnetizing coils.

Though the magnetization of an element by subjection to the magneticfield within a coil does not require that the field be maintained forany extended period of time, and may be attained almost instantaneouslyby an electrical impulse of very short duration, the current flow duringthat short interval must in most instances be very heavy, in order toassure the development of a sufficiently intense magnetic field toattain the desired magnetizing action. This high amperage current flowhas in the past proven very difiicult to control because of the problemsencountered in attempting to devise a switch or relay capable ofinstantaneously closing the coil energizing circuit without causingrapid pitting or burning of the switch or relay contacts by the heavyflow of current, and the resultant sparking between the contacts duringclosure. These contacts therefore have been capable of functioning foronly a very short active life, and have been unreliable andunpredictable in operation at all times.

A major object of the present invention is to provide improved circuitfor energizing and de-energizing a magnetizing coil or otherelectrically operated unit, with the circuit being especiallyconstructed to positively avoid damage to the controlling contacts, eventhough the current passed through those contacts may be relatively high.Certain particular features of the invention relate to the constructionand manner of energization of a relay which is utilized in the overallcircuit of the invention for opening and closing the circuit to the coilor other electrically Y operated unit.

In accordance with the teachings of the invention, the coil of thecircuit closing relay is energized by alternating current, desirably 60cycle, 110 volt. A.C. The relay is so constructed, and the energizingpotential and frequency are so selected, that the coil when energized isnot effective to pull the movable contact or contacts of the relay toclosed position as positively as is desired in most relay arrangements.Instead, the movable contact or contacts are purposely left free tovibrate through a very substantial range of movement relative to thestationary contacts while the relay is closed. More particularly, themovable contacts vibrate or oscillate at the frequency of the energizingcurrent, that is, usually 60 cycles per second. This vibratory motioncauses the movable contacts to continuously and repeatedly shiftrelative to and over the surface of the engaged stationary contactswhile the relay is closed, to in this way actually mechanicallypolishthe engaging surfaces of the contacts, in a manner continuously guardingagainst the development of any pits or other irregularities in thesurfaces ,of the contacts. It is found that these vibratory relaycontacts can be closed and opened under heavy load conditions repeatedlyand almost indefinitely without adversely affecting their currentcarrying capacity, and without pitting of or other damage to thecontacts.

To attain the above discussed results, the relay may be of aconstruction essentially similar to that customarily employed for directcurrent relays, but with this direct current type of relay beingenergized by alternating current, as discussed above, and preferably ofa voltage substantially higher than would be employed if the relay wereunder direct current operation. Structurally, the relay should haveconsiderably less stationary iron or other stationary magnetic materialthan is present in most alternating current relays, so that the magneticcircuit provided for the flux is not of a great enough flux carryingcapacity to smooth over the irregularities of the alternating currentsupply, and thus maintain the contacts in tightly closed non-vibratorycondition.

The above and other features and objects of the invention will be betterunderstood from the following detailed description of the typicalembodiment illustrated in the accompanying drawing, in which:

FIG. 1 illustrates somewhat diagrammatically and in perspective amagnetizing device constructed in accordance with the invention;

FIG. 2 shows the electrical circuit of the Fig. 1 magnetizer;

FIG. 3 illustrates, partially in elevation and partially in section, arelay of the type preferably utilized in the FIG. 2 circuit;

FIG. 4 is a plan view of the FIG. 3 relay, taken on line 44 of FIG. 3;and

FIG. 5 is a fragmentary vertical section taken on line 5-5 of FIG. 4.

Referring first to FIG. 1, I have illustrated at 10 a magnetizing coilwhich is wound helically about an axis 11, and is hollow to enable theinsertion into the interior of the coil of an element 12 which is to bemagnetized by electrical energization of the coil. The coil receiveshigh amperage current from a control box 13 through two electrical leads14 and 15. Power is supplied to control box 13 through a cord 16 fromany appropriate source of alternating current diagrammaticallyrepresented at 17 in'FIG. 2, with the two conductors in cord 16 beingdesignated 18 and 19 in FIG. 2. Preferably, as previously stated, thepower source 17 is volt, 60 cycle per second, alternating current.

The control box 13 contains a full wave rectifying circuit 20, to theinput side of which power source 17 is connected, by connection of lead19 to the rectifier circuit at 21, and connection of lead 18 to therectifier circuit through a two-Way manually operated control switch 22and a line 23 leading to input terminal 24. The result ing directcurrent leaves the rectifier circuit through two leads 25 and 26, acrosswhich two capacitors 27 and 28 are connected in parallel, with aresistor 29 preferably being connected into lead 26 between therectifier and the capacitors.

- Capacitors 27 and 28 may typically have a value of 6,000 microfarad,Volt DC, while the resistor 29 may typically have a rating of 8 ohms, 18watts.

An indicator light 30 is shunted across the input side of rectifiercircuit 20, to indicate when the movable contact 31 of switch 22 is inits upper position for supplying alternating current to the rectifiercircuit, and thus charging capacitors 27 and 28. A voltmeter 32 isconnected across the capacitors, to indicate the amount of the chargewhich has been attained on the capacitors, so that an operator canreadily tell when the charge is suflicient to call for discharging thecapacitors through the magnetizin g coil 10.

This discharging of the capacitors is controlled by downward actuationof the movable contact 31 of switch 22, to close through that switch acircuit leading from alternating current power source 17 to coil 33 of acontrol relay 34. The movable contact 35 of relay 34 is actuablemagnetically to closed position with respect to a pair of contacts 36and 37 by energization of coil 33, to thus close a discharge circuitfrom capacitors 27 and 28 to magnetizing coil through leads 14- and 15.

With reference now to FIGS. 3 to 5, which show a preferred constructionfor relay 34, it is noted that coil.

33 of this relay may consist of a large number of turns of wire wound inmany layers about an inner tube 38 formed of non-magnetic material, suchas an appropriate brass or the like. The coil may thus form anessentially annular structure, as illustrated in FIG. 3, with acylindrical hollow housing or outer covering 39 being disposed about theperiphery of the coil, and being concentric with coil 33 and tube 38,all being centered about a main vertical axis 40 of the relay. Housing39 may be rigidly brazed, welded, or otherwise secured to a transversebottom wall 41 extending across the bottom of the coil and tube 38, andhaving ears or tabs 42 by which the coil may be mounted to a supportingstructure 43. The upper end of housing 39 may be closed, about tube 38,by one or a pair of essentially annular discs 43, whose inner edges mayengage tube 38 at 44, and which discs 43' may be secured rigidly to anupper flange 45 of housing 39 and a non-magnetic and non-electricallyconductive top member 46 by screws 47. Members 46 may be formed of anappropriate plastic material.

The armature 48 of the relay may be externally cylindrical and centeredabout axis 40, and be a fairly close fit within the interior of tube 38,so that the armature 48 is magnetically actuable downwardly by coil 33from the full line position of FIG. 1 to the broken line position ofthat figure. This armature 48 is of course formed of an appropriatemagnetic material, such as iron. The upper end of armature or plunger 48may have an annular flange 49 engageable downwardly against the upperend of tube 38 to limit downward movement of the armature. Also, thearmature may rigidly carry an upwardly projecting reduced diameterportion 50, and a still smaller diameter portion 51, which resilientlyand shiftably carry the movable contact or cross head 35 which engagesstationary contacts 36 and 37 of the relay. Movable contact 35 isnormally held in the full line position of FIG. 3 relative to theplunger, by an upper spring 52 which is confined between movablecontacts 35 and an upper enlargement 53 carried by the armature, withthis spring 52 coacting with a second and lower spring 54 confinedbetween the upper side of the plunger and movable contact 35. These twosprings are insulated from contact 35 by an annular non-conductivegrommet structure 55, mounted wtihin an aperture in contact 35. Thesprings of course act together to yieldingly urge the armature andmovable contact upwardly to the normally open full line position of FIG.3.

Contact 35 is elongated in a left to right direction as viewed in FIG.3, and has two contact surfaces 56 formed at its opposite ends, andfacing downwardly for engagement with inverted contact surfaces 57 ofthe two stationary contacts 36 and 37. The stationary contacts areconnected by straps 58 to terminals 59 by which the stationary contactsare connected into the FIG. 2 circuit.

The resilient movement of contact 35 relative to stationary contacts 36and 37 is limited by a pair of upstanding block portions or bosses 60 ofthe nonconduotive member 46. These two bosses project upwardly atopposite sides of contact 35, as brought out in FIGS. 4 and 5, and haveinner parallel vertical planar surfaces 61 which are spaced slightlyoutwardly from the opposite parallel side edges 62 of contact 35, sothat the contact 35 is free for some lateral movement, and is free forlimited turning movement about vertical axis 40, but

both of these types of movement are definitely limited by engagement ofedges 62 with boss surfaces 61.

The various electrical and magnetic parameters of relay 34, and thevoltage and frequency of the alternating current which energizes coil 33of this relay, are all so selected and predetermined as to attain anautomatic polishing action between contact 35 and the engaged contacts36 and 37, whenever coil 33 is energized to pull armature 48 downwardly.More particularly, the energizing voltage and current are sufi'icient topull armature 48 and its resiliently carried movable contact 35downwardly from the full line position of FIG. 3 to the broken lineposition of that figure, whenever coil 33 is energized by thealternating current supplied to input lines 18 and 19. However, theholding action of the coil with respect to armature 48 is purposelyreduced to a minimum value which, though holding contact 35substantially closed, will still allow that contact to vibrate relativeto stationary contacts 36 and 37 through a very substantial and easilyvisible range of movement, preferably at least as much as about onesixty-fourth of an inch '(also desirably through a distance at leastabout as great as 5% of the maximum dimension of each contact face, i.e.5% of the maximum dimension of the actual contacting portion of faces 56and 57), so that faces 56 of the movable contacts repeatedly andcontinuously wipe across and vibrate relative faces 57 of the stationarycontacts to effectively polish all of these contact faces and maintainthem in optimum current transmitting condition. The vibratory motionthus attained can be observed to produce different types of movement ofthe movable contact 37, so that the movable contact faces 56 and 57 movehorizontally across the upper surfaces of contact faces 57, and may inmany instances follow a somewhat circular path in wiping across surfaces57, with different portions of contact 35 moving alternately intoengagement with the two edges 61 of the motion limiting bosses, and withthe springs 52 and 54 facilitating the vibratory motion because of theirresilient mounting of movable contact 35 relative to the armature orplunger.

To describe briefly a cycle of operation of the circuit of FIG. 2,assume that switch 22 is initially in its intermediate open position,and that the element 12 of FIG. 1 is inserted into coil 10 to a positionat which it is to be magnetized by the coil. An operator then movescontact 31 of the switch 22 upwardly to energize the rectifier clrcuit20, so that direct current is supplied to capacitors 27 and 28, tocharge them. When voltmeter 32 indicates that an appropriate charge hasbeen attained on the capacitors, the movable contact of switch 22 isactuated downwardly to open the circuit to the rectifier arrangement,and close the circuit to coil 33 of the relay. The alternating currentwithin coil 33 thus pulls anmature 48 and the connected movable contact35 downwardly to close the discharge circuit between stationary contacts36 and 37, so that the capacitors 27 and 28 suddenly discharge throughthe contacts of the relay to magnetizing coil 10, to attain the desiredmagnetizing action. The discussed vibratory motion of contact 35relative to stationary contacts 36 and 37 polishes all of these contactsin the manner discussed, and prevents development of pits or craters onthe contact surfaces, so that the relay may be repeatedly opened andclosed through many cycles, and almost indefinitely, withoutencountering the contact deterioration or damage which is a customaryproblem in magnetizers and other equipment of the discussed generaltype.

Obviously, many variations may be made in the structure of the relay andits relationship to the energizing alternating current while stillattaining the discussed contact vibrating effect. No attempt will bemade to set forth all of these diiferent possible variations of theinvention since persons versed in the electrical field will be able todevise apparatus embodying the invention from the above teachings. Someof the parameters which may be altered to achieve and. control vibrationof movable contact 35 of the relay are the particular construction ofcoil 33, the ELmOlJIItJOfEStHlIlOIJEIIY magnetic material associatedwith the coil and typically constituting the parts 39, 41, '43 and 45,,the size, cross section, and flux capacity of this sta tionary magneticmaterial as compared with the movable magnetic material of armature 48,the magnetic retentivity of the magnetic material, the strength ofsprings 52 and 54, and the voltage and frequency of the energizing alternating current. A characteristic which is especially important is thementioned feature, relating to the amount of stationary magneticmaterial associated with the coil. In this connection, it is noted thatthe coil is preferably free of the relatively large amount of stationarylaminated iron or other magnetic material which is normally present inan alternating current coil, and which usually provides in analternating current coil a substantially complete magnetic circuitentirely about the coil of very great flux carrying capacity. Desirably,no such laminations are present in the relay utilized in my invention,or if any laminations are present they have a flux capacity which is notgreat enough to prevent vibration of contact 35.

For best results, the stationary magnetic material is essentiallynon-retentive or soft magnetically (i.e. has a minimum magneticretentivity), and for this purpose may typically be formed of soft ironor the like. Also, it is preferred that the stationary magneticmaterial, if any is present in the main magnetic actuating circuit ofthe relay, be sulfciently limited in cross section to have a maximumflux capacity (along that circuit) which is not greater than the maximumflux capacity of the armature along the circuit, and preferably notgreater than about 40% of that armature flux capacity. For purposes ofthis limitation, the magnetic circuit in FIG. 3 may extend verticallywithin the armature, then horizontally or radially through plates 43,then vertically through housing 39, horizontally through plate 41 andupwardly through a stationary core 148 if such is present (with all ofthe elements 43, 39, 41 and 148 typically being of magnetic material butpreferably of fairly small flux capacity as indicated). As will beapparent the effective flux capacity of the stationary parts is ofcourse determined by and equal to the capacity of that portion of thestationary material which is most poorly conductive magnetically andwhich therefore defines the minimum flux capacity point along thestationary flux path. Similarly the minimum flux capacity portion of thearmature determines the effective overall capacity of that part.

I claim:

1. Apparatus comprising capacitor means, means for charging saidcapacitor means, a unit to be energized by discharge of said capacitormeans, a discharge controlling relay having a coil and having contactsconnected into a discharge circuit from said capacitor means to saidunit, said contacts including a first contact and a second contactmovable relative thereto into circuit closing engagement with the firstcontact by energization of said coil, and means for supplyingalternating current of a predetermined voltage to said relay coil toclose said contacts and thereby discharge said capacitor means to saidunit, said relay being constructed to vibrate said second contact verysubstantially when energized by said predetermined voltage ofalternating current and to an extent repeatedly and continually shiftingsaid second contact relative to the other contact while the contacts areclosed to thereby mechanically polish the contacts and prevent pittingthereof.

2. Apparatus as recited in claim 1, in which said unit is a magnetizingcoil for magnetizing an element in the vicinity thereof upon dischargeof said capacitor means.

3. Apparatus as recited in claim 1, in which said charging means includea rectifier circuit energizable by alternating current and operable tosupply direct current to said capacitor means.

4. Apparatus as recited in claim 1, in which said charging means includea rectifier circuit energizable by alternating current and operable tosupply direct current to said capacitor means, said means for supplyingalternating current to said relay coil including switch means forsuccessively connecting a common source of alternating current first tosaid rectifier circuit to charge the capacitor means, and then to saidrelay coil to discharge the capacitor means through said contacts.

5. Apparatus as recited in claim 1, in which said relay is constructedto vibrate said second contact through a distance as great as onesixty-fourth of an inch relative to the other contact while the contactsare closed.

6. Apparatus as recited in claim 1, in which said relay has an armatureconnected to said movable contact to actuate it and projecting into andmovable axially within said coil.

7. Apparatus as recited in claim 1, in which said relay has an armatureconnected to said movable contact to actuate it and projecting into andmovable axially within said coil, and means connecting said movablecontact to said armature resiliently.

8. Apparatus as recited in claim 1, in which said relay has a movablearmature formed of magnetic material for actuating said movable contact,and in which, if any stationary magnetic material is present in themagnetic circuit of the relay, said stationary material does not have aflux capacity along said circuit over about 40% of the flux capacity ofsaid armature therealong.

9. Apparatus as recited in claim 1, in which said relay has a magneticmaterial armature connected to said movable contact to actuate it andprojecting into and movable axially within said coil, said movablecontact being a cross head disposed transversely of the axis of the coilat the outside thereof and engageable at opposite ends with two of saidfirst contacts to close said discharge circuit, spring means connectingsaid cross head to said armature shiftably and resiliently and enablingsome lateral movement of the cross head transversely of said axis, saidrelay having stationary magnetic material near the coil in sufficientquantity to hold the movable contact essentially closed when the coil isenergized but not suflicient to prevent said vibration.

10. Apparatus as recited in claim '9, in which said unit is amagnetizing coil, said charging means including a rectifier circuitenergizable by alternating current and operable to supply direct currentto said capacitor means, said means for supplying alternating current tosaid relay coil including switch means for successively connecting acommon source of alternating current first to said rectifier circuit tocharge the capacitor means, and then to said relay coil to discharge thecapacitor means through said contacts.

11. The combination comprising a relay including a coil to be energizedby alternating current of a predetermined voltage, a first contact, anda second contact actuable relative to the first contact into circuitclosing engagement with the first contact by energization of said coil,and means for supplying alternating current of said predeterminedvoltage to said coil, said relay being constnucted to vibrate saidsecond contact very substantially when energized by said predeterminedvoltage of alternating current and to an extent repeatedly andcontinually shifting said second contact relative to the other contactwhile the contacts are closed to thereby mechanically polish thecontacts and prevent pitting thereof.

12. Apparatus as recited in claim 11, in which said relay is constructedto vibrate said second contact relative to the other contact while thecontacts are closed through a distance as great as 5% of the maximumdimension of the contacting faces of said contacts.

13. Apparatus as recited in claim 11, in which said relay has anarmature connected to said second contact to actuate it and projectinginto and movable axially within said coil.

14. Apparatus as recited in claim 11, in which said relay has a movablearmature formed of magnetic material for actuating said second contact,and in which, if any stationary magnetic material is present in themagnetic circuit of the relay, said stationary material does not have aflux capacity along said circuit over about 40% of the flux capacity ofsaid armature therealong.

15. Apparatus as recited in claim 11, in which said relay has a magneticmaterial armature connected to said second contact to actuate it andprojecting into and movable axially Within said coil, said secondcontact being a cross head disposed transversely of the axis of the coilat the outside thereof and engageable at opposite ends with two of saidfirst contacts, spring means connecting said cross head to said armatureshiftably and resiliently and enabling some lateral movement of thecross head traversely of said axis, said relay having stationarymagnetic material near the coil in sufficient quantity to hold thesecond contact essentially closed when the coil is energized but notsufiicient to prevent said vibration. 7

References Cited STATES PATENTS UNITED 1,466,654 8/1923 Clough 307-137 X2,157,640 5/1939 Swarthout 307138 X 2,817,774 12/1957 Kniel et al. 307-137 3,248,633 4/1968 Guarrera 317-451 X LEE T. I-HX, Primary Examiner.

11. THE COMBINATION COMPRISING A RELAY INCLUDING A COIL TO BE ENERGIZEDBY ALTERNATING CURRENT OF A PREDETERMINED VOLTAGE, A FIRST CONTACT, ANDA SECOND CONTACT ACTUABLE RELATIVE TO THE FIRST CONTACT INTO CIRCUITCLOSING ENGAGEMENT WITH THE FIRST CONTACT BY ENERGIZATION OF SAID COIL,AND MEANS FOR SUPPLYING ALTERNATING CURRENT OF SAID PREDETERMINEDVOLTAGE TO SAID COIL, SAID RELAY BEING CONSTRUCTED TO VIBRATE SAIDSECOND CONTACT VERY SUBSTANTIALLY